The present invention relates to a printing machine. More particularly this invention concerns an arrangement for axially reciprocating the rubbing rollers of the inking mechanism in a printing machine.
A printing machine is known having a plurality of inking rollers which distribute ink or the like from a supply through so-called rubbing rollers onto an impression or form roller or cylinder that itself prints on the paper or similar workpiece to be printed. Since the inking density of material to be printed varies over the length of the material to be printed and since the printing or form roller or cylinder is normally provided with an axially extending groove that takes on no ink, it is necessary to spread the ink on this form roller in such a manner as to achieve the most uniform possible printing results.
It has been suggested in this context to axially reciprocate the rubbing rollers in order to best distribute the ink on the form cylinder in the most efficient manner. To this end the axially reciprocal rubbing rollers may be connected, for instance to a hydraulic arrangement which reciprocates all of them synchronously. In such an arrangement it is possible to vary the stroke and the speed of reciprocation, but not the angular phase of the rubbing rollers relative to the form roller. Thus, such an arrangement makes it impossible to achieve carefully controlled printing results.
It has also been suggested to provide a cam control arrangement which reciprocates the rubbing rollers. Such an arrangement has the disadvantage that the ink distribution is sinusoidal and cannot be controlled with any degree of accuracy.
Further arrangements have been suggested to synchronize the axial reciprocation of the rubbing rollers relative to the form roller. Such arrangements, however, do not allow the machine to be set up to achieve particular printing results, as all of the rollers work together and there is virtually no manner to determine exactly what inking characteristic will be obtained.
Various prior-art printing arrangements are shown in U.S. Pat. No. 3,345,941, British Pat. No. 828,825, and German published specification No. 2,228,939.